Recognising Bletchley Park's unsung heroines

This recent photo shows a rebuilt Colossus machine. It took 14 years to rebuild because of a lack of information on how the 2,500-valve machine fitted together. Bombe has also been rebuilt after 12 years of work.

At the end of the war, all the original Colossi and Bombes were dismantled and secretly discarded, mostly by their female operatives, on the command of Winston Churchill so that other countries could learn nothing of Britain's codebreaking efforts.